xref: /art/disassembler/disassembler_x86.cc

/*
 * Copyright (C) 2012 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "disassembler_x86.h"

#include "stringprintf.h"

#include <stdint.h>
#include <iostream>

namespace art {
namespace x86 {

DisassemblerX86::DisassemblerX86() {
}

void DisassemblerX86::Dump(std::ostream& os, const uint8_t* begin, const uint8_t* end) {
  size_t length = 0;
  for (const uint8_t* cur = begin; cur < end; cur += length) {
    length = DumpInstruction(os, cur);
  }
}

static const char* gReg8Names[]  = { "al", "cl", "dl", "bl", "ah", "ch", "dh", "bh" };
static const char* gReg16Names[] = { "ax", "cx", "dx", "bx", "sp", "bp", "di", "si" };
static const char* gReg32Names[] = { "eax", "ecx", "edx", "ebx", "esp", "ebp", "edi", "esi" };

static void DumpReg0(std::ostream& os, uint8_t /*rex*/, size_t reg,
                     bool byte_operand, uint8_t size_override) {
  DCHECK_LT(reg, 8u);
  // TODO: combine rex into size
  size_t size = byte_operand ? 1 : (size_override == 0x66 ? 2 : 4);
  switch (size) {
    case 1: os << gReg8Names[reg]; break;
    case 2: os << gReg16Names[reg]; break;
    case 4: os << gReg32Names[reg]; break;
    default: LOG(FATAL) << "unexpected size " << size;
  }
}

static void DumpReg(std::ostream& os, uint8_t rex, uint8_t reg,
                    bool byte_operand, uint8_t size_override) {
  size_t reg_num = reg;  // TODO: combine with REX.R on 64bit
  DumpReg0(os, rex, reg_num, byte_operand, size_override);
}

static void DumpBaseReg(std::ostream& os, uint8_t rex, uint8_t reg,
                        bool byte_operand, uint8_t size_override) {
  size_t reg_num = reg;  // TODO: combine with REX.B on 64bit
  DumpReg0(os, rex, reg_num, byte_operand, size_override);
}

static void DumpIndexReg(std::ostream& os, uint8_t rex, uint8_t reg,
                         bool byte_operand, uint8_t size_override) {
  int reg_num = reg;  // TODO: combine with REX.X on 64bit
  DumpReg0(os, rex, reg_num, byte_operand, size_override);
}

static void DumpSegmentOverride(std::ostream& os, uint8_t segment_prefix) {
  switch (segment_prefix) {
    case 0x2E: os << "cs:"; break;
    case 0x36: os << "ss:"; break;
    case 0x3E: os << "ds:"; break;
    case 0x26: os << "es:"; break;
    case 0x64: os << "fs:"; break;
    case 0x65: os << "gs:"; break;
    default: break;
  }
}

size_t DisassemblerX86::DumpInstruction(std::ostream& os, const uint8_t* instr) {
  const uint8_t* begin_instr = instr;
  bool have_prefixes = true;
  uint8_t prefix[4] = {0, 0, 0, 0};
  const char** modrm_opcodes = NULL;
  do {
    switch (*instr) {
      // Group 1 - lock and repeat prefixes:
      case 0xF0:
      case 0xF2:
      case 0xF3:
        prefix[0] = *instr;
        break;
        // Group 2 - segment override prefixes:
      case 0x2E:
      case 0x36:
      case 0x3E:
      case 0x26:
      case 0x64:
      case 0x65:
        prefix[1] = *instr;
        break;
        // Group 3 - operand size override:
      case 0x66:
        prefix[2] = *instr;
        break;
        // Group 4 - address size override:
      case 0x67:
        prefix[3] = *instr;
        break;
      default:
        have_prefixes = false;
        break;
    }
    if (have_prefixes) {
      instr++;
    }
  } while (have_prefixes);
  uint8_t rex = (*instr >= 0x40 && *instr <= 0x4F) ? *instr : 0;
  bool has_modrm = false;
  bool reg_is_opcode = false;
  size_t immediate_bytes = 0;
  size_t branch_bytes = 0;
  std::ostringstream opcode;
  bool store = false;  // stores to memory (ie rm is on the left)
  bool load = false;  // loads from memory (ie rm is on the right)
  bool byte_operand = false;
  bool ax = false;  // implicit use of ax
  bool reg_in_opcode = false;  // low 3-bits of opcode encode register parameter
  switch (*instr) {
#define DISASSEMBLER_ENTRY(opname, \
                     rm8_r8, rm32_r32, \
                     r8_rm8, r32_rm32, \
                     ax8_i8, ax32_i32) \
  case rm8_r8:   opcode << #opname; store = true; has_modrm = true; byte_operand = true; break; \
  case rm32_r32: opcode << #opname; store = true; has_modrm = true; break; \
  case r8_rm8:   opcode << #opname; load = true; has_modrm = true; byte_operand = true; break; \
  case r32_rm32: opcode << #opname; load = true; has_modrm = true; break; \
  case ax8_i8:   opcode << #opname; ax = true; immediate_bytes = 1; byte_operand = true; break; \
  case ax32_i32: opcode << #opname; ax = true; immediate_bytes = 4; break;

DISASSEMBLER_ENTRY(add,
  0x00 /* RegMem8/Reg8 */,     0x01 /* RegMem32/Reg32 */,
  0x02 /* Reg8/RegMem8 */,     0x03 /* Reg32/RegMem32 */,
  0x04 /* Rax8/imm8 opcode */, 0x05 /* Rax32/imm32 */)
DISASSEMBLER_ENTRY(or,
  0x08 /* RegMem8/Reg8 */,     0x09 /* RegMem32/Reg32 */,
  0x0A /* Reg8/RegMem8 */,     0x0B /* Reg32/RegMem32 */,
  0x0C /* Rax8/imm8 opcode */, 0x0D /* Rax32/imm32 */)
DISASSEMBLER_ENTRY(adc,
  0x10 /* RegMem8/Reg8 */,     0x11 /* RegMem32/Reg32 */,
  0x12 /* Reg8/RegMem8 */,     0x13 /* Reg32/RegMem32 */,
  0x14 /* Rax8/imm8 opcode */, 0x15 /* Rax32/imm32 */)
DISASSEMBLER_ENTRY(sbb,
  0x18 /* RegMem8/Reg8 */,     0x19 /* RegMem32/Reg32 */,
  0x1A /* Reg8/RegMem8 */,     0x1B /* Reg32/RegMem32 */,
  0x1C /* Rax8/imm8 opcode */, 0x1D /* Rax32/imm32 */)
DISASSEMBLER_ENTRY(and,
  0x20 /* RegMem8/Reg8 */,     0x21 /* RegMem32/Reg32 */,
  0x22 /* Reg8/RegMem8 */,     0x23 /* Reg32/RegMem32 */,
  0x24 /* Rax8/imm8 opcode */, 0x25 /* Rax32/imm32 */)
DISASSEMBLER_ENTRY(sub,
  0x28 /* RegMem8/Reg8 */,     0x29 /* RegMem32/Reg32 */,
  0x2A /* Reg8/RegMem8 */,     0x2B /* Reg32/RegMem32 */,
  0x2C /* Rax8/imm8 opcode */, 0x2D /* Rax32/imm32 */)
DISASSEMBLER_ENTRY(xor,
  0x30 /* RegMem8/Reg8 */,     0x31 /* RegMem32/Reg32 */,
  0x32 /* Reg8/RegMem8 */,     0x33 /* Reg32/RegMem32 */,
  0x34 /* Rax8/imm8 opcode */, 0x35 /* Rax32/imm32 */)
DISASSEMBLER_ENTRY(cmp,
  0x38 /* RegMem8/Reg8 */,     0x39 /* RegMem32/Reg32 */,
  0x3A /* Reg8/RegMem8 */,     0x3B /* Reg32/RegMem32 */,
  0x3C /* Rax8/imm8 opcode */, 0x3D /* Rax32/imm32 */)

#undef DISASSEMBLER_ENTRY
  case 0x50: case 0x51: case 0x52: case 0x53: case 0x54: case 0x55: case 0x56: case 0x57:
    opcode << "push";
    reg_in_opcode = true;
    break;
  case 0x58: case 0x59: case 0x5A: case 0x5B: case 0x5C: case 0x5D: case 0x5E: case 0x5F:
    opcode << "pop";
    reg_in_opcode = true;
    break;
  case 0x68: opcode << "push"; immediate_bytes = 4; break;
  case 0x6A: opcode << "push"; immediate_bytes = 1; break;
  case 0x70: case 0x71: case 0x72: case 0x73: case 0x74: case 0x75: case 0x76: case 0x77:
  case 0x78: case 0x79: case 0x7A: case 0x7B: case 0x7C: case 0x7D: case 0x7E: case 0x7F:
    static const char* condition_codes[] =
    {"o", "no", "b/nae/c", "nb/ae/nc", "z/eq", "nz/ne", "be/na", "nbe/a",
     "s", "ns", "p/pe",    "np/po",    "l/nge","nl/ge", "le/ng", "nle/g"
    };
    opcode << "j" << condition_codes[*instr & 0xF];
    branch_bytes = 1;
    break;
  case 0x88: opcode << "mov"; store = true; has_modrm = true; byte_operand = true; break;
  case 0x89: opcode << "mov"; store = true; has_modrm = true; break;
  case 0x8A: opcode << "mov"; load = true; has_modrm = true; byte_operand = true; break;
  case 0x8B: opcode << "mov"; load = true; has_modrm = true; break;

  case 0x0F:  // 2 byte extended opcode
    instr++;
    switch (*instr) {
      case 0x38:  // 3 byte extended opcode
        opcode << StringPrintf("unknown opcode '0F 38 %02X'", *instr);
        break;
      case 0x3A:  // 3 byte extended opcode
        opcode << StringPrintf("unknown opcode '0F 3A %02X'", *instr);
        break;
      case 0x80: case 0x81: case 0x82: case 0x83: case 0x84: case 0x85: case 0x86: case 0x87:
      case 0x88: case 0x89: case 0x8A: case 0x8B: case 0x8C: case 0x8D: case 0x8E: case 0x8F:
        opcode << "j" << condition_codes[*instr & 0xF];
        branch_bytes = 4;
        break;
      default:
        opcode << StringPrintf("unknown opcode '0F %02X'", *instr);
        break;
    }
    break;
  case 0x80: case 0x81: case 0x82: case 0x83:
    static const char* x80_opcodes[] = {"add", "or", "adc", "sbb", "and", "sub", "xor", "cmp"};
    modrm_opcodes = x80_opcodes;
    has_modrm = true;
    reg_is_opcode = true;
    store = true;
    byte_operand = (*instr & 1) == 0;
    immediate_bytes = *instr == 0x81 ? 4 : 1;
    break;
  case 0xB0: case 0xB1: case 0xB2: case 0xB3: case 0xB4: case 0xB5: case 0xB6: case 0xB7:
    opcode << "mov";
    immediate_bytes = 1;
    reg_in_opcode = true;
    break;
  case 0xB8: case 0xB9: case 0xBA: case 0xBB: case 0xBC: case 0xBD: case 0xBE: case 0xBF:
    opcode << "mov";
    immediate_bytes = 4;
    reg_in_opcode = true;
    break;
  case 0xC3: opcode << "ret"; break;
  case 0xE9: opcode << "jmp"; branch_bytes = 4; break;
  case 0xEB: opcode << "jmp"; branch_bytes = 1; break;
  case 0xFF:
    static const char* ff_opcodes[] = {"inc", "dec", "call", "call", "jmp", "jmp", "push", "unknown-ff"};
    modrm_opcodes = ff_opcodes;
    has_modrm = true;
    reg_is_opcode = true;
    load = true;
    break;
  default:
    opcode << StringPrintf("unknown opcode '%02X'", *instr);
    break;
  }
  std::ostringstream args;
  if (reg_in_opcode) {
    DCHECK(!has_modrm);
    DumpReg(args, rex, *instr & 0x7, false, prefix[2]);
  }
  instr++;
  if (has_modrm) {
    uint8_t modrm = *instr;
    instr++;
    uint8_t mod = modrm >> 6;
    uint8_t reg_or_opcode = (modrm >> 3) & 7;
    uint8_t rm = modrm & 7;
    std::ostringstream address;
    if (mod == 0 && rm == 5) {  // fixed address
      address << StringPrintf("[0x%X]", *reinterpret_cast<const uint32_t*>(instr));
      instr += 4;
    } else if (rm == 4 && mod != 3) {  // SIB
      uint8_t sib = *instr;
      instr++;
      uint8_t ss = (sib >> 6) & 3;
      uint8_t index = (sib >> 3) & 7;
      uint8_t base = sib & 7;
      address << "[";
      if (base != 5 || mod != 0) {
        DumpBaseReg(address, rex, base, byte_operand, prefix[2]);
        if (index != 4) {
          address << " + ";
        }
      }
      if (index != 4) {
        DumpIndexReg(address, rex, index, byte_operand, prefix[2]);
        if (ss != 0) {
          address << StringPrintf(" * %d", 1 << ss);
        }
      }
      if (mod == 1) {
        address << StringPrintf(" + %d", *reinterpret_cast<const int8_t*>(instr));
        instr++;
      } else if (mod == 2) {
        address << StringPrintf(" + %d", *reinterpret_cast<const int32_t*>(instr));
        instr += 4;
      }
      address << "]";
    } else {
      if (mod != 3) {
        address << "[";
      }
      DumpBaseReg(address, rex, rm, byte_operand, prefix[2]);
      if (mod == 1) {
        address << StringPrintf(" + %d", *reinterpret_cast<const int8_t*>(instr));
        instr++;
      } else if (mod == 2) {
        address << StringPrintf(" + %d", *reinterpret_cast<const int32_t*>(instr));
        instr += 4;
      }
      if (mod != 3) {
        address << "]";
      }
    }

    if (reg_is_opcode) {
      opcode << modrm_opcodes[reg_or_opcode];
    }
    if (load) {
      if (!reg_is_opcode) {
        DumpReg(args, rex, reg_or_opcode, byte_operand, prefix[2]);
        args << ", ";
      }
      DumpSegmentOverride(args, prefix[1]);
      args << address.str();
    } else {
      DCHECK(store);
      DumpSegmentOverride(args, prefix[1]);
      args << address.str();
      if (!reg_is_opcode) {
        args << ", ";
        DumpReg(args, rex, reg_or_opcode, byte_operand, prefix[2]);
      }
    }
  }
  if (ax) {
    DumpReg(args, rex, 0 /* EAX */, byte_operand, prefix[2]);
  }
  if (immediate_bytes > 0) {
    if (has_modrm || reg_in_opcode || ax) {
      args << ", ";
    }
    if (immediate_bytes == 1) {
      args << StringPrintf("%d", *reinterpret_cast<const int8_t*>(instr));
      instr++;
    } else {
      CHECK_EQ(immediate_bytes, 4u);
      args << StringPrintf("%d", *reinterpret_cast<const int32_t*>(instr));
      instr += 4;
    }
  } else if (branch_bytes > 0) {
    DCHECK(!has_modrm);
    int32_t displacement;
    if (branch_bytes == 1) {
      displacement = *reinterpret_cast<const int8_t*>(instr);
      instr++;
    } else {
      CHECK_EQ(branch_bytes, 4u);
      displacement = *reinterpret_cast<const int32_t*>(instr);
      instr += 4;
    }
    args << StringPrintf("%d (%p)", displacement, instr + displacement);
  }
  os << StringPrintf("\t\t\t%p: ", begin_instr);
  for (size_t i = 0; begin_instr + i < instr; ++i) {
    os << StringPrintf("%02X", begin_instr[i]);
  }
  os << StringPrintf("\t%-7s ", opcode.str().c_str()) << args.str() << std::endl;
  return instr - begin_instr;
}

}  // namespace x86
}  // namespace art